1. Field of the Invention
The present invention relates to a technology for accessing data.
2. Description of the Related Art
When a plurality of access devices that read and write data are connected to a single data recording device, the matching of the data recorded to and held in the data recording device must be maintained between access devices. Various technologies have been disclosed in the past to this end.
Japanese Laid-Open Patent Application H8-153014 discloses processing that is performed when one of a plurality of client devices which share a solid state disk device (or SSD: Solid State Drive) writes data to the SSD. Here, lock processing is performed to declare that this client device has acquired a file management information right to the SSD, after which the data writing is carried out. Once the data writing is finished, the client device performs unlock processing and relinquishes the file management information right.
With the method in Japanese Laid-Open Patent Application H8-153014, a plurality of access devices (that is, client devices) perform mutually exclusive processing when data is written to a single data recording device, modified, etc. This exclusive processing prevents plural sets of data from being written to the data recording device, modified, etc., at the same time.
In the field of communications technology, there is a known technique in which out of a plurality of communication devices connected to a communication line, only a communication device having an exclusive right, which specifies the communication device that is allowed to send data to a communication network (hereinafter also called a data control right or host right), actively sends data, or proactively controls communication. In this case, setting the host right is a specific way to achieve a kind of exclusive control.
However, the following problem can occur when one communication device has the host right, and another communication device forcibly takes back this host right at some point in time.
The right to send data to a communication network and so forth is managed along with transfer of the host right. Thus, although matching is maintained for the communication network as a whole, the communication device that relinquishes the host right ends up having its content that is being processed interrupted when its host right is taken away. If this interrupted content processing involves data writing, modification, reading, or the like performed at the data recording device shared among communication devices, there is the possibility that matching of the data will not be preserved.
In view of this, it is an object of the present invention to maintain data matching even when access to the data recording device, etc., is interrupted.